The Daily Air Quality Index (DAQI) is determined by the highest concentration of five key pollutants:
The pollution concentrations are divided into bands to give an individual index for each pollutant based on the atmospheric concentration.
| Pollutant | Band 1 | Band 2 | Band 3 | Band 4 | Band 5 | Band 6 | Band 7 | Band 8 | Band 9 | Band 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Ozone µg/m3 | 0-33 | 34-66 | 67-100 | 101-120 | 121-140 | 141-160 | 161-187 | 188-213 | 214-240 | 241 or more |
| Nitrogen Dioxide µg/m3 | 0-67 | 68-134 | 135-200 | 201-267 | 268-334 | 335-400 | 401-467 | 468-534 | 535-600 | 601 or more |
| Sulphur Dioxide µg/m3 | 0-88 | 89-177 | 178-266 | 267-354 | 355-443 | 444-532 | 533-710 | 711-887 | 888-1,064 | 1,065 or more |
| PM2.5 Particles µg/m3 | 0-11 | 12-23 | 24-35 | 36-41 | 42-47 | 48-53 | 54-58 | 59-64 | 65-70 | 71 or more |
| PM10 Particles µg/m3 | 0-16 | 17-33 | 34-50 | 51-58 | 59-66 | 67-75 | 76-83 | 84-91 | 92-100 | 101 or more |
Pollutant underline colours are those used on the Monitoring sites graphs.
The overall DAQI is the highest band of any individual pollutant. So, for example, if Ozone was in Band 3 and the others were in Band 2, then the DAQI would be 3. But if Ozone was 3 and Nitrogen Dioxide was in Band 4, then the DAQI would be 4.